Report 728001031/2005
Meeting the EU 2°C climate target:
global and regional emission
implications
M.G.J. den Elzen*
M. Meinshausen**
* Corresponding author: Netherlands Environmental Assessment Agency (MNP associated with the
RIVM), PO Box 1, 3720 BA Bilthoven, The Netherlands, e-mail: michel.den.elzen@mnp.nl; tel
+31 30 2744584; fax: +31 30 2744464
** Swiss Federal Institute of Technology (ETH Zurich), Environmental Science Department,
Rämistrasse 101,CH-8092 Zurich, Switzerland, e-mail: malte.meinshausen@env.ethz.ch.
At present, visiting scientist at: Climate and Global Dynamics Division, National Center for
Atmospheric Research (NCAR), P.O. Box 3000, Boulder, CO 80307-3000, USA.
This research was performed with the support of the Dutch Ministry of Housing, Spatial
Planning and the Environment as part of the International Climate Change Policy Project
(M/728001 Internationaal Klimaatbeleid)
Netherlands Environmental Assessment Agency (MNP associated with the RIVM), PO Box 303,
3720 AH Bilthoven, The Netherlands, telephone: +31 30 274 274 5, website: www.mnp.nl
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Abstract
Meeting the EU 2°C climate target: global and regional emission implications
This report presents a set of multi-gas emission pathways for different CO2-equivalent
concentration stabilization levels, i.e. 400, 450, 500 and 550 ppm CO2-equivalent, along with
an analysis of their global and regional reduction implications and implied probability of
achieving the EU climate target of 2°C. The effect of different assumptions made for
baselines, technological improvement rates, or delay of global action on the resulting
emission pathways is also analysed. For achieving the 2°C target with a probability of more
than 60%, greenhouse gas concentrations need to be stabilized at 450 ppm CO2-equivalent or
below, if the 90% uncertainty range for climate sensitivity is believed to be 1.5 to 4.5°C. A
stabilization at 450 (400) ppm CO2-equivalent requires global emissions to peak around
2015, followed by substantial overall reductions in the order of 30% (50%) compared to
1990 levels in 2050. In 2020, Annex I emissions need to be approximately 15% (30%) below
1990 levels. Non-Annex I emissions may increase compare to the 1990 levels, but not
compared to their baseline emissions (15-20% reduction). A further delay in peaking of
global emissions by 10 years doubles maximum reduction rates to about 5% per year, and
very likely leads to high costs. In order to keep the option open of stabilising at 400 and
450 ppm CO2 equivalent, the USA and major advanced non-Annex I countries will have to
participate in an agreement aimed at reductions within 10-15 years.
Keys words: multi-gas emission pathway, climate target, post-2012 commitments
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Rapport in het kort
Het behalen van de EU 2 graden klimaatdoelstelling: mondiale en regionale emissie
implicaties
Dit rapport presenteert mondiale broeikasgas emissiepaden die leiden tot stabilisatie van de
concentraties van de broeikasgassen op verschillende niveaus, i.e. 400, 450, 500 and 550
ppm CO2-equivalent. Daarnaast analyseert dit rapport de benodigde regionale en mondiale
broeikasgas emissiereducties en de waarschijnlijkheden voor het behalen van de EU 2 graden
doelstelling. Ook wordt het effect van verschillende veronderstellingen ten aanzien van
baseline emissie scenario’s, technologische verbeteringen en vertragingen in het stabiliseren
van de mondiale emissies op de uiteindelijke emissiepaden geanalyseerd. Om een zekerheid
van meer dan 60% te hebben dat de EU 2 graden doelstelling wordt gehaald, dienen de
broeikasgas concentraties gestabiliseerd te worden op het niveau van 450 ppm CO2equivalent of minder (400 ppm), als het 90%-onzekerheidsinterval voor de
klimaatgevoeligheid tussen de 1,5 en 4,5°C ligt. De mondiale emissies zouden daartoe rond
2015 hun maximum bereikt dienen te hebben, gevolgd door substantiële emissiereducties in
de orde van 30% (50%) in 2050. Om de mondiale emissies binnen 20 jaar hun maximale
niveau te laten bereiken zijn in 2020 verdergaande emissiereducties van de industrielanden
nodig, in de order van 15% (30%) onder het 1990-niveau. De ontwikkelingslanden mogen
hun emissies laten groeien ten opzichte van het 1990-niveau, maar zullen moeten reduceren
ten opzichte van hun baseline (15-20%). Een verder uitstel van het stabiliseren van de
mondiale emissies met meer dan 10 jaar verdubbelt de maximale mondiale
reductiesnelheden tot meer dan 5% per jaar, en zal mogelijk leiden tot hoge kosten. Verder
zal om de concentratie stabilisatiedoelstellingen van 400 en 450 ppm te halen, het
noodzakelijk zijn dat de VS en de voornaamste ontwikkelingslanden hun emissies moeten
gaan reduceren binnen 10-15 jaar.
Trefwoorden: multi-gas emissiepaden, klimaatdoelstelling target, post-2012
lastenverdelingen
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Acknowledgements
This study was performed within the framework of International Climate Change Policy
Support project (M/728001 Internationaal Klimaatbeleid). We would like to thank our
colleagues, in particular Marcel Berk, Bas Eickhout, Paul Lucas and Detlef van Vuuren
(MNP), as well as Bill Hare from the PIK Institute in Germany, for their comments and
contributions. Finally, we thank Ruth de Wijs for language editing assistance. Any errors in
the report are the responsibility of the authors.
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Contents
1
INTRODUCTION ....................................................................................................6
2
METHOD FOR DEVELOPING EMISSION PATHWAYS WITH COST-EFFECTIVE
MULTI-GAS MIXES ................................................................................................9
3
EMISSION PATHWAYS AND THEIR TRANSIENT TEMPERATURE IMPLICATIONS 15
3.1
3.2
3.3
CO2-equivalent concentration and radiative forcing..................................................... 15
Temperature increase .................................................................................................... 16
Emission pathways........................................................................................................ 18
4
GLOBAL EMISSION ABATEMENT COSTS ............................................................20
5
THE REGIONAL EMISSION IMPLICATIONS .........................................................22
6
THE IMPACT OF FURTHER DELAY IN EMISSION REDUCTIONS...........................26
6.1
6.2
7
Delay in peaking of global emissions ........................................................................... 26
The impact of a further delay in USA involvement in emission reductions ................. 27
CONCLUSIONS ....................................................................................................30
REFERENCES .........................................................................................................................32
APPENDIX A
DESCRIPTION OF THE EMISSION PATHWAYS CALCULATION ...................36
APPENDIX B
SOURCE OF INFORMATION ON MARGINAL ABATEMENT COSTS ...............38
APPENDIX C
GLOBAL GREENHOUSE GAS EMISSIONS OF THE PATHWAYS PRESENTED 39
APPENDIX D
COMPARISON WITH IMAGE 2.2 MULTI-GAS EMISSION PATHWAYS.......40
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1 Introduction
The aim of this study is to explore allowable emissions levels of the set of the six greenhouse
gases covered under the Kyoto Protocol in the long and short term that are compatible with
any long-term climate policy targets to avoid dangerous climate change. In order to
determine allowable levels of greenhouse gas emissions, we have to back-calculate from
acceptable levels of climate change to emissions. This is not simple. Apart from the question
of what an acceptable level of climate change constitutes – a political issue – there are major
scientific uncertainties in the cause–effect chain. This is the relationship between levels of
greenhouse gas emissions and the impacts related to the human-induced climate change.
Thus, we take a pragmatic route: the point of departure of our analysis will be the long-term
EU climate target of limiting the global mean temperature increase to 2°C above preindustrial levels (1861-1890), as adopted in 1996, and recently (March 2005) reconfirmed by
the European Council (1996; 2005). It should be kept in mind though that 2°C cannot be
regarded as harm-free or ‘safe’, as shown by many reviews in the scientific literature (Smith
et al., 2001; Hare, 2003; ACIA, 2004; Hitz and Smith, 2004). For example, the humaninduced climate change up to the present has already doubled the risk of heat waves, such as
the European heat wave of 2003 and the resulting unusually large numbers of heat-related
deaths (Allen and Lord, 2004; Stott et al., 2004).
To deal with the large uncertainties in the cause-effect chain we have adopted a probabilistic
approach and focus on the uncertainty in climate sensitivity. Climate sensitivity summarizes
the key uncertainties for long-term climate projections and is expressed as the expected
warming of the earth’s surface for a doubling of pre-industrial CO2 concentrations
(2x278=556ppm). Several studies have estimated probability density functions1 for climate
sensitivity, of which we select two as examples: Firstly, the one by Wigley and Raper
(2001), which is built to match the conventional IPCC 1.5 to 4.5oC uncertainty range, and
secondly a recent estimate derived by Murphy et al. (2004) using a large ensemble of GCM
runs.
We developed multi-gas abatement pathways and analysed the associated risks2 of them
overshooting the EU climate target of 2°C (Hare and Meinshausen, 2004; Meinshausen,
2005). Earlier analysis of emission pathways leading to climate stabilization focuses mainly
on CO2 only (Enting et al., 1994; Wigley et al., 1996; Swart et al., 1998; Hourcade and
Shukla, 2001). Consistent information on reduction potential for the non-CO2 gases has been
lacking for a long time, which is why most studies on the implications of a multi-gas
reduction strategy are more recent (see e.g. Reilly et al., 1999; Eickhout et al., 2003).
Reducing non-CO2 emissions can have important advantages in terms of avoiding climate
impacts (Hansen et al., 2000; Meinshausen et al., 2004; Wigley et al., submitted). Recent
studies exploring the impacts of including non-CO2 gases in the analysis of the Kyoto
Protocol have found that major cost reductions can initially be obtained through the
relatively cheap abatement options for some of the non-CO2 gases and the increase in
flexibility (Hayhoe et al., 1999; Reilly et al., 1999). Multi-gas studies on long-term
stabilization targets also show considerably lower costs for a multi-gas strategy than under a
1
These probability density functions provide information on how likely the real climate sensitivity can be
found in a certain interval.
2
Note that throughout this report, the term ‘risk of overshooting’ is used for the ‘probability of exceeding
a threshold’. Technically speaking, ‘risk’ is used in this respect to describe the product of likelihood and
consequence with ‘consequence’ described as a step function with the value 0 below and 1 above the threshold
(Meinshausen, 2005).
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CO2-only strategy (e.g., Tol, 1999; Manne and Richels, 2001; van Vuuren et al., 2003;
2004). However, the time-dependent share of non-CO2 gases depends on the use of 100-year
Global Warming Potentials (GWPs) (e.g., van Vuuren et al., 2005). Under a multi-gas
strategy using the 100-year GWPs, the contribution of the non-CO2 gases in total reductions
is very large early in the scenario period (50-60% in the first two decades (e.g., van Vuuren
et al., 2003; 2004), although CO2 remains by far the most important human-induced radiative
forcing agent in the long term. Not using GWPs (but instead determining the substitution on
the basis of cost-effectiveness in realizing a long-term target) implies that the primary focus
of mitigation in the near-term rests on CO2 (e.g., Manne and Richels, 2001) Other studies
have explored the methodological issues of a multi-gas approach, such as which type of
climate targets (for instance, concentration or temperature targets) can best be set for such a
diverse group of gases (see Manne and Richels, 2001; Richels et al., 2004; Fuglestvedt et al.,
2003; O'Neill, 2003).
Obviously, it is much more complicated to define emission pathways for stabilising CO2equivalent concentrations3 than for CO2 only, because these can be reached through various
combinations of greenhouse gases, which also have different contributions to the total
radiative forcing over time. So far, there are roughly five ways of accounting for non-CO2
emissions:
(i)
simple scenario assumptions, for example, the common non-intervention
scenario4 (SRES A1B) for non-CO2 emissions in the IPCC Third Assessment
Report (Cubasch et al., 2001) or a certain CO2-equivalent concentration (e.g.
100 ppm) to be added to a CO2-concentration stabilization target (Eickhout et al.,
2003);
(ii)
‘scaling’, concentrations or radiative forcing, which are proportionally scaled
with CO2: e.g. 23% of CO2 forcing (see Raper and Cubasch, 1996);
(iii) accounting for source-specific reduction potentials for all gases, as in the postSRES scenarios (Morita et al., 2000; Swart et al., 2002),
(iv)
different approaches assuming cost-optimal implementation of available
reduction options over the greenhouse gases, sources and regions (van Vuuren et
al., 2003) and/or over time (Manne and Richels, 2001) and
(v)
meta-approaches that make use of the multi-gas characteristics in existing
scenarios derived by any of the previous approaches (e.g., Meinshausen, 2004).
Here we focus on a cost-optimisation variant (iv), which closely reflects the political reality
of pre-set caps on aggregated emissions and individual cost-optimising actors. Specifically,
the actors are assumed to choose a cost-minimizing mix of reductions across the different
greenhouse gases to achieve the preset global emission level for each five year period.
Further on in this study we will focus on the development of multi-gas emission pathways
for the lower concentration stabilization targets (400, 450, 500 and 550 ppm CO2-eq.), as
opposed to 550 and 650 ppm CO2-eq. as in our earlier study on emission pathways (Eickhout
3
‘CO2 equivalence’ summarises the climate effect (‘radiative forcing’) of all human-induced greenhouse
gases, tropospheric ozone and aerosols, following the IPCC definition, as if we only changed the atmospheric
concentrations of CO2 (see Schimel et al., 1997).
4
Following the terminology of Meinshausen et al. (2004), we can draw a distinction here between
scenarios and emission pathways. While the emission pathway focus solely on emissions, a scenario represents
a more complete description of possible future states of the world, including their socio-economic
characteristics and energy and transport infrastructures. According to this definition, many of the existing
‘scenarios’ are in fact pathways, including the ones derived in this study.
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et al., 2003)5, so as to achieve more certainty in reaching the EU 2 degree Celsius target
(e.g., Hare and Meinshausen, 2004). For these lower concentration targets, we assume a
certain overshooting (or peaking), i.e. concentrations may first increase to an ‘overshooting’
concentration level up to 480, 500 and 525 ppm then decrease before stabilizing at 400, 450
and 500 ppm CO2-equivalence, respectively. This overshooting is partially reasoned by the
already substantial present concentration levels and the attempt to avoid drastic sudden
reductions in the presented emission pathways.
This study also explores the step that succeeds the development of global emission
pathways: i.e. the issue of differentiating post-2012 commitments, in other words, how to
allocate the global emission reduction on a regional level. This quantitative analysis of
allocation-based regime proposals is based on earlier work (e.g. den Elzen et al., 2005a;
2005b).
The analysis here focuses on four questions for climate-change policy-making:
1. What are the emission pathways compatible meeting the EU two degree Celsius
target, and what is the certainty of achieving this?
2. What is the effect of different assumptions made for the baseline and technological
improvement rates of abatement potential and costs on the emission pathways, and
their resulting emissions reductions and abatement costs?
3. What are the global and regional emission reduction implications?
4. What are the implications of a further delay in mitigation actions?
The next chapter presents the overall method used for this analysis of linking global emission
pathways with climate targets. Chapter 3 contains the results of the analysis for various
concentration stabilization targets, and analyses the impact of some of the major
uncertainties (question 1). Chapter 4 presents the global abatement costs (question 2), while
Chapter 5 analyses the regional emission implications based on a post-2012 climate regime
for future commitments (question 3). Chapter 6 analyses questions with regard to the effects
of a delay in emission reductions. The final chapter (Chapter 7) draws up several
conclusions.
5
These emission pathways were used in the EU research project ‘Greenhouse gas reduction pathways in
the UNFCC post-Kyoto process up to 2025’, which forthwith will be known as the GRP study (Criqui et al.,
2003).
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2 Method for developing emission pathways with costeffective multi-gas mixes
In order to assess the emission implications of different stabilization levels, this study
presents new multi-gas emission pathways for the scenario period, 2000-2400, derived by a
method for a cost-effective mitigation of emissions. This method calculates the cost-optimal
mixes of greenhouse gas emission reductions for a given global emission pathway. The
emission pathway is determined iteratively to match prescribed climate targets of any level,
as described in detail below. It should be kept in mind though that this approach does not
derive cost-effective pathways over the whole scenario period per se, but focuses on a costeffective split among different greenhouse gas reductions for given emission limitations on
GWP-weighted and aggregated emissions. For example, based on the current model version
with static cost assumptions, we cannot make definitive judgments on how a delay in global
action will affect overall mitigation costs over time. However, the model framework surely
accommodates an analysis of the existing policy framework with preset caps on Global
Warming Potential (GWP)-weighted overall emissions under the assumption of costminimizing national strategies. The emissions that have been adapted to meet the pre-defined
stabilization targets include those of all major greenhouse gases (fossil CO2, CH4, N2O,
HFCs, PFCs and SF6, i.e. the so-called six Kyoto greenhouse gases), ozone precursors
(VOC, CO and NOx) and sulphur aerosols (SO2).
For our method we used the policy decision support tool FAIR 2.0 in combination with
another climate policy tool called SiMCaP.
The FAIR (Framework to Assess International Regimes for the differentiation of
commitments) 2.0 model developed at the National Institute for Public Health and the
Environment (RIVM) in the Netherlands (www.mnp.nl/fair) is a policy decision-support tool,
which aims to assess the environmental and abatement costs implications of climate regimes
for differentiation of post-2012 commitments (den Elzen and Lucas, 2003; 2005). For the
calculation of the emission pathways, only the (multi-gas) abatement costs model of FAIR is
used. This model distributes the difference between baseline and global emission pathway
over the different regions, gases and sources following a least-cost approach, taking full
advantage of the flexible Kyoto Mechanisms (emissions trading) (see den Elzen et al.,
2005b). For this purpose, it makes use of (time-dependent) Marginal Abatement Cost (MAC)
curves6 for the different regions, gases and sources as described below. The FAIR model also
uses baseline scenarios, i.e. potential greenhouse gas emissions in the absence of climate
policies, from the integrated assessment model IMAGE7 and the energy model, TIMER.8
The SiMCaP (‘Simple Model for Climate Policy Assessment’) developed at the ETH in
Zurich, Switzerland (www.simcap.org). The SiMCaP pathfinder module makes use of an
iterative procedure to find emission paths that correspond to a predefined arbitrary climate
6
MAC curves that reflect the costs of abating the last ton of CO2-equivalent emissions and, in this way,
describe the potential and costs of the different abatement options considered are used here.
7
The IMAGE 2.2 model is an integrated assessment model consisting of a set of integrated models that
together describe important elements of the long-term dynamics of global environmental change, such as
agriculture and energy use, atmospheric emissions of greenhouse gases and air pollutants, climate change, landuse change and environmental impacts (IMAGE-team, 2001) (www.mnp.nl/image).
8
The global energy model TIMER 1.0, as part IMAGE, describes the primary and secondary demand and
production of energy and the related emissions of greenhouse gases and on a regional scale (17 world regions)
(de Vries et al., 2002).
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target. The global climate calculations make use of the simple climate model, MAGICC 4.1
(Wigley and Raper, 2001; 2002; Wigley, 2003). More specifically, the pathfinder module of
SiMCaP makes use of an iterative procedure to find emission paths that correspond to a
predefined arbitrary climate target.9
The integration of both models, the ‘FAIRSiMCaP’ 1.0 model, allows the strengths of both
models to be combined to: (i) calculate the cost-optimal mixes of greenhouse gas reductions
for a global emissions profile under a least costs approach (FAIR) and (ii) find the global
emissions profile that is compatible with any arbitrary climate target (SiMCaP).
More specifically, the FAIRSiMCaP calculations consist of four steps (Figure 1):
1. Using the SiMCaP model to construct a parameterised global CO2-equivalent emission
pathway, which is here defined by sections of linear decreasing or increasing emission
reduction rates RI (initial 2010 value), Rx, Ry and Rz and years (X, Y and Z) at which the
reduction rates change (see for a detailed description of the methodology Appendix A). This
CO2-equivalent emission pathway10 includes the anthropogenic emissions of six Kyoto
greenhouse gases. One exception is formed by the LUCF (land use and land use change
related) CO2 emissions; this because no MAC curves are available for these, although the
option of sink-related uptakes is parameterised in FAIR as one mitigation option. The LUCF
CO2 emissions are described by the baseline scenario. Up to 2012, the pathway incorporates
the implementation of the Annex I Kyoto Protocol targets for the Annex I regions excluding
Australia and the USA.11 Although the USA follows the proposed greenhouse-gas intensity
target (White-House, 2002), this leads to emissions which do not significantly differ from
their baseline emissions (van Vuuren et al., 2002).
2. The abatement costs model of FAIR is used to allocate the global emissions reduction
objective (except LUCF CO2 emissions): i.e. the difference between the baseline emissions
and the global CO2-equivalent emission pathway (see Figure 2) of step 1. Here a least-cost
approach (cost-optimal allocation of reduction measures) is used for five year intervals over
the 2000-210012 period for the six Kyoto greenhouse gases; 100-year GWP indices, different
numbers of sources (e.g. for CO2: 12; CH4: 9; N2O: 7) and seventeen world regions13 are
employed, taking full advantage of the flexible Kyoto Mechanisms – International Emissions
Trading (IET), Joint Implementation (JI) and the Clean Development Mechanism (CDM).
9
For further details such as assumptions with regard to natural forcing, see Meinshausen et al. (2004).
The global baseline and emission pathways are expressed in CO2-equivalent emissions, calculated using
the emissions of the six greenhouse gases combined with the 100-year Global Warming Potentials (GWPs)
(IPCC, 2001). Despite its limitations, the GWP concept is used here in a manner consistent with the current
practices in policy documents, such as in the Kyoto Protocol.
11
Here, we do not analyse the impact of other implementations of the Kyoto Protocol on the final emission
pathways: i.e. (1) a ‘strong’ Kyoto implementation, in which the USA and Australia also implement their Kyoto
targets and the emissions of economies in transition (Russia and Eastern European countries) follow the lower
of their Kyoto targets and their baseline emissions, and their ‘hot air’ will not be sold, or a ‘failure’ of the
Kyoto Protocol, in which all countries implement their baseline emissions, since implementation of both cases
does not seem very realistic politically. The impact of these Kyoto implementations on the global CO2 emission
pathways aiming at 400, 450 and 550 ppm CO2-only stabilization was analysed by Höhne (2005).
12
After 2100, there are no marginal abatement cost estimates, but another methodology is followed. More
specifically, the CO2 equivalent emission reductions rates are assumed to apply to each individual gas, except
where non-reducible fractions (0.7) have been defined (N2O, CH4).
13
Calculations were done for 17 regions, i.e. Canada, USA, OECD-Europe, Eastern Europe, FSU, Oceania
and Japan (Annex I regions); Central America, South America, the Middle East and Turkey (middle- and highincome non-Annex I regions); Northern Africa, Southern Africa, East Asia (incl. China) and South-East Asia
(low-middle income non-Annex I regions); Western Africa, Eastern Africa and South Asia (incl. India) (lowincome non-Annex I regions) (IMAGE-team, 2001).
10
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Figure 2 shows the contribution of the different greenhouse gases in the global emissions
reduction to, in this case, reach the 450 ppm CO2-equivalent concentration level. The figure
clearly shows that up to 2025, there are potentially large incentives for sinks and non-CO2
abatement options (cheap options), so that the non-CO2 reductions and sinks form a
relatively large share in the total reductions. Later in the scenario period, the focus is more
on the CO2 reductions, and the contribution of most gases becomes more proportional to
their share in baseline emissions. The emission pathways of the different greenhouse gases
can then be constructed in this way.
Figure 1. The FAIRSiMCaP model. The calculated global emission pathways were
developed by using an iterative procedure as implemented in SiMCaP’s ‘pathfinder’ module,
using MAGICC to calculate the global climate indicators, the multi-gas abatement costs and
the FAIR model to allocate the emissions of the individual greenhouse gases and the IMAGE
2.2 and TIMER model for the baseline emissions scenarios along with the MAC curves.
Different sets of baseline- and time-dependent MAC curves for different emission sources
are used here. For energy- and industry-related CO2 emissions (energy, feedstock and cement
production), the impulse response curves calculated with the energy model, TIMER 1.0 (de
Vries et al., 2002) are used. This energy model calculates regional energy consumption,
energy-efficiency improvements, fuel substitution, and the supply and trade of fossil fuels
and renewable energy technologies, as well as carbon capture and storage. A carbon tax on
fossil fuels is imposed for constructing the MAC curves to induce emission abatements,
taking into account technological developments, learning effects and system inertia (van
Vuuren et al., 2004a). The TIMER response curves were calculated assuming a linear
increase of the permit price after the first commitment period and the final value in the
evaluation year. In this way, the MAC curves do take into account (as a first-order
approximation) the time pathway of earlier abatement, although not dynamically. For CO2
sinks the MAC curves of the IMAGE model are used (van Vuuren et al., 2004b).
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For non-CO2, exogenously determined MAC curves from EMF-21 (DeAngelo et al., 2004;
Delhotal et al., 2004; Schaefer et al., 2004) are used. This set is based on detailed abatement
options, and includes curves for CH4 and N2O emissions from both energy- and industryrelated emissions and some agricultural sources, as well as abatement options for the
halocarbons (see Appendix B). The non-CO2 MACs were constructed mainly for 2010, and
do not include technological improvements in time. Furthermore, the curves were
constructed against a hypothetical baseline that assumes that no measures are taken in the
absence of climate policy (‘frozen emission factors’). Therefore, the non-CO2 MAC curves
have been corrected for measures already applied under our baseline scenario; this is to
increase consistency within the analysis (see van Vuuren et al., 2003 for the methodology
used). Finally, increases are assumed in the abatement potentials due to the technology
process and removal of implementation barriers. Here, a relatively conservative value of an
increasing potential (at constant costs) due to technology progress and removal of
implementation barriers for all other non-CO2 MAC curves of 0.4% per year is assumed
(simply incorporated by multiplying the MAC curves by this technological rate, as illustrated
in Figure 3 (Graus et al., 2004; van Vuuren et al., 2004b). There are still some remaining
agricultural emission sources of CH4 and N2O, where no MAC curves were available (e.g.
for N2O agricultural waste burning, indirect fertiliser, animal waste and domestic sewage).
As it is unlikely that these sources will remain unabated under ambitious climate targets, we
assumed a linear reduction towards a maximum of 35% compared to baseline levels within a
period of 30 years (2040).
CO2 -eq . emissions in Gt C-eq
25
a
450
20
baseline B 1
10 0
%-cont ribut ion t ot al red uct ion (%)
b
75
15
50
10
25
5
IM A -B 1
0
19 95
2 020
IM A -B 1
204 5
20 70
2 095
CO2 -eq . emissions in Gt C-eq
25
450
b aseline CPI
0
20 10
10 0
c
20
203 5
Sinks
F-gasses
N2O
CH 4
CO2
20 60
208 5
%-cont ribut ion t ot al red uct ion (%)
d
75
15
50
10
25
5
C P I-tech
0
19 95
2 020
CP I-tech
204 5
20 70
2 095
0
20 10
203 5
Sinks
F-gasses
N2O
CH4
CO2
20 60
208 5
Figure 2. Contribution of greenhouse gases in total emission reductios under the emission
pathways for a stabilization at 450ppm CO2-equivalent concentration of the IMA-B1 (a,b)
and CPI+tech scenario (c,d).
Finally, in addition to the end-of-pipe measures, as summarized in the non-CO2 MAC
curves, CH4 and N2O emissions can also be reduced by systemic changes in the energy
system (for instance, the reduction in the use of coal and/or gas reduce CH4 emissions during
production and transport of these fuels). As seen in van Vuuren et al. (2004b) we account for
these effects by a coupled analysis of the FAIR and TIMER models. It should be noted,
however, that the total impact of these indirect reductions are relatively small (a maximum of
about 0.1-0.2 GtC) (compared to the overall reduction objective of more than 10 GtC in
2050) and have therefore not been taken into account in the analysis here. For a detailed
description of the MAC curves we refer to van Vuuren et al. (2004a; 2004b).
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3. The greenhouse gas concentrations, and global temperature and sea level rise are
calculated using the simple climate model MAGICC 4.1.
4. Within the iterative procedure of the SiMCaP model, the parameterizations of the CO2equivalent emission pathway (step 1) are optimized (repeat step 1, 2 and 3) until the climate
output and the prescribed target show sufficient matches.
Reduction costs (US$/tC)
100
80
Technology
development :
Bending MACs
outward
60
40
Already included
in baseline
20
Fraction reduced
0
0.2
0.4
0.6
0.8
1
-20
Figure 3: Incorporation of Marginal Abatement Curves in FAIR 2.0 (van Vuuren et al.,
2004b). Note: The marginal abatement curves are corrected for the improvements already
assumed in the baseline scenario, and bend outward in time as a result of technology
development.
These emission pathways have been developed for three underlying baseline scenarios:
1. CPI: the Common POLES IMAGE (CPI) baseline (van Vuuren et al., 2003; van Vuuren et
al., 2004b) scenario with the fixed LUCF CO2 emissions of this scenario (Appendix C) and
with the default MAC curves . The CPI scenario assumes a continued process of
globalization, medium technology development and a strong dependence on fossil fuels. This
corresponds to a medium-level emissions scenario when compared to the IPCC SRES
emissions scenarios (Figure 2c).
2. CPI+tech: the CPI baseline scenario with the fixed LUCF CO2 emissions of the IMA-B1
scenario (less deforestation) and with MAC curves assuming additional technological
improvements. As current studies (e.g., Azar et al., 2004; Nakicenovic and Riahi, 2003)
indicate that more technological improvements in abatement potential and reduction costs
are possible than assumed in the CPI baseline, we have analyzed the impact of more
optimistic assumptions. For this, we made the following, rather arbitrary, assumptions: (1)
for the MAC curves of energy CO2, an additional technological improvement factor of
0.2%/year; (2) for the MAC curves of the non-CO2 gases, a technological improvement rate
of 1%/year instead of 0.2%/year and (3) for the sources of non-CO2 gases, where no MAC
curves were available, a maximum reduction of 80% instead of 30% in 2040.
3. IMA-B1: the IMAGE IPCC SRES B1 baseline (IMAGE-team, 2001) scenario with the
fixed LUCF CO2 emissions of this scenario and the default MAC curves (Appendix C). This
scenario assumes continuing globalisation and economic growth, and a focus on the social
and environmental aspects of life. The baseline emissions are given in Figure 2a;
The CPI scenario has been selected as this is a medium-level emissions scenario, also used in
our earlier study (Eickhout et al., 2003) and the GRP study (Criqui et al., 2003). Here, two
Netherlands Environmental Assessment Agency
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additional baselines, namely CPI+tech and IMAGE B1 have been selected for two reasons.
First of all, emissions are uncertain and the two scenarios explore the situation of more
optimistic improvements of the abatement potential and reduction costs. Secondly, there
might be reasons why climate policies could inevitably shift the ‘baseline’, i.e. the
development of future emissions in case no further climate policies were undertaken. The
method used in our study intends to capture these effects, but may underestimate its
consequences. In addition, there is some evidence that technological ‘lock-in’ effects might
cause low-emissions paths being achievable at very low additional costs (Gritsevskyi and
Nakicenovic, 2000). Obviously, with lower baseline scenarios, it will be easier to achieve
ambitious mitigation pathways. In fact, the combination of the CPI baseline and the standard
set of MAC curves renders the derivation of 450 and 400 ppm CO2-equivalent stabilization
levels impossible.
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3 Emission pathways and their transient temperature
implications
3.1 CO2-equivalent concentration and radiative forcing
This chapter presents various global multi-gas emission pathways for stabilization at CO2equivalence levels14 of 550 ppm (3.65W/m2), 500ppm (3.14W/m2), 450 ppm (2.58W/m2) and
400 ppm (1.95W/m2). The latter three pathways are assumed to peak at 525 ppm
(3.40W/m2), 500 ppm (3.14W/m2) and 480 ppm (2.92W/m2) before they return to their
ultimate stabilization levels around 2150 (Figures 4 and 5). This peaking is partially reasoned
by the already substantial present net forcing levels (Hare and Meinshausen, 2004) and the
attempt to avoid drastic sudden reductions in the emission pathways presented. These lower
two stabilization pathways are within the range of the lower mitigation scenarios in the
literature (Swart et al., 2002; Nakicenovic and Riahi, 2003; Azar et al., 2004; Hare and
Meinshausen, 2004) (Figure 5).
Figure 4. The contribution to net radiative forcing by the different forcing agents under the
three default emission pathways for a stabilization at (a,d) 550, (b,e) 450 and (c,f) 400 ppm
CO2-equivalent concentration after peaking at (b,e) 500 and (c,f) 475 ppm, respectively for
the (a-c) CPI+tech and (d-f) IMA B1 baseline scenarios. The upper line of the stacked area
graph represents net human-induced radiative forcing. The net cooling due to the direct and
indirect effect of SOx aerosols and aerosols from biomass burning is depicted by the lower
negative boundary, on top of which the positive forcing contributions are stacked (from
bottom to top) by CO2, CH4, N2O, fluorinated gases (including the cooling effect due to
stratospheric ozone depletion), tropospheric ozone and the combined effect of fossil organic
and black carbon.
14
As previously mentioned the CO2-equivalent concentration is based on radiative forcing of all
greenhouse gases, tropospheric ozone and aerosols, but not natural forcings (solar and volcanic forcing),
whereas in our earlier study in Eickhout et al. (2003) CO2-equivalent concentration is based on the radiative
forcing of only the six Kyoto greenhouse gases. The impact of this difference together with other differences
(some already discussed before, i.e. lower final concentration levels, peaking concentration strategy) on the
final emission pathways will be discussed in Appendix D.
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Figure 5 also shows CO2-equivalent concentration profiles corresponding with a range of
CO2 concentration profiles due to different baselines and abatement potentials and costs. For
example, 550 CO2-eq. corresponds approximately with 475-500 CO2 ppm, and 400 ppm
CO2-eq. corresponds with 350-375 ppm CO2 only. As previously mentioned, no emission
pathways for 450 and 400 ppm CO2-eq. level were derived for the CPI baseline.
Figure 5. The CO2 (a) and CO2-equivalent (b) concentrations for the stabilization pathways
at 550, 500, 450 and 400 ppm CO2-equivalent concentrations for the three baseline
scenarios (CPI, CPI+tech and IMA-B1). For comparison, the concentration implications of
the IPCC-SRES non-mitigation scenarios (grey dotted lines) and the lower range of
published mitigation scenarios (Azar et al., 2004; Nakicenovic and Riahi, 2003; Swart et al.,
2002) (grey solid lines) are also plotted (see details in Hare and Meinshausen, 2004).
3.2 Temperature increase
Figure 6a shows the probabilistic temperature implications of the overshoot concentration
profiles based on the climate sensitivity PDF of Wigley and Raper (2001)15, for the emission
pathways under the B1 scenario.16 In these transient calculations, we included the natural
forcings (i.e. solar and volcanic forcings) (see for more details, Hare and Meinshausen,
2004).17 The results under the other scenarios are similar.
15
The PDF of Wigley and Raper (2001) assumes the conventional 1.5 to 4.5°C climate sensitivity
uncertainty range as being a 90% confidence interval of a lognormal PDF.
16
The temperature projection for the emission pathway for 550 ppm CO2-eq. for the median is already
above 2 degree Celsius in 2100, which seems in contrast with the temperature projection below 2 degree
Celsius of the emission pathway in 2100 for a stabilization at 550 ppm CO2-eq. of our earlier study (Eickhout et
al., 2003). The reasons for our higher projection now are: (i) the natural forcing that contributes about 0.2 to
0.3°C, if assuming the last 20-year average of solar forcing and the last 100 years of volcanic forcing, which are
assumed here; (ii) the higher emissions in our emission pathway for 550 ppm CO2-eq, and (iii) the use of a
median estimate of 2.6°C climate sensitivity (instead of 2.5°C). Appendix D compares the emission pathways
presented here in more detail with those of our earlier study.
17
An exception has been made for the calculations on the risk of overshooting the 2°C target in
equilibrium. There, equilibrium temperatures have been directly derived from anthropogenic radiative forcings
(Hare and Meinshausen, 2004) (see, for example, Figure 6 - the number on the white arrows).
Netherlands Environmental Assessment Agency
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Due to the inertia of the climate system, the peak of radiative forcing (3.14W/m2) before
stabilization at 450 ppm CO2-eq. (2.58W/m2) does not translate into a comparable peak in
global mean temperatures. However, for the 400 ppm CO2-eq. stabilization pathway
presented, the initial peak at 480ppm CO2-eq. seems to be decisive with regard to the
question of whether the 2°C or any other temperature threshold will be crossed (Figure 6).
Figure 6a shows that for a stabilization at 550 ppm CO2-eq. (corresponding approximately to
a 475 ppm CO2 only stabilization), the risk of overshooting 3°C is still about 33%. There is
even a risk of about 10% that 4°C is exceeded. The probability that warming exceeds 2°C is
very high, approximately 75%. For the long-term stabilization at 500 ppm CO2-eq.
(approximately 450 ppm CO2 stabilization) too, the probability of exceeding 2°C is likely,
about 60% (not shown). Only for a stabilization at 400 ppm CO2-eq. (approximately 350-375
ppm CO2 stabilization) and, to a lesser extent, at 450 ppm CO2-eq. (about 400 ppm CO2 only
stabilization), is the possibility of equilibrium warming exceeding 2°C strongly reduced, to
less than about 13% and 40%, respectively. If a different uncertainty distribution is assumed,
for example, the one by Murphy et al. (2004), the risk still sharply decreases with lower
stabilization levels, although the risk of overshooting generally increases. Specifically,
stabilization at 450 ppm CO2-eq. would imply a risk of overshooting 2°C of about 78% (see
Figure 6b).
a
b
Figure 6. The probabilistic temperature implications for the stabilization pathways at (a)
550 ppm, (b) 450 ppm and (c) 400 ppm CO2-equivalent concentrations for the B1 baseline
scenario based on the climate sensitivity PDF by Wigley and Raper (2001) (IPCC
lognormal) (top row) and the PDF by Murphy et al. (2004) (bottom row). Shown are the
median (solid lines) and 90% confidence interval boundaries (dashed lines), as well as the
1%,10%,33%,66%,90%, and 99% percentiles (borders of shaded areas). The historical
temperature record and its uncertainty from 1900 to 2001 is shown (grey shaded band)
(Folland et al., 2001).
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3.3 Emission pathways
The emissions of the pathways for stabilization at 550, 450 and 400 ppm CO2-eq.
concentrations can be summarized in their GWP-weighted sum of six Kyoto gases
emissions, as illustrated in Figure 7. Clearly, there are different pathways that can lead to the
ultimate stabilization level. Here, we assume that the global emission reduction rates should
not exceed an annual reduction of 2.5%/year for all default pathways (at least not over longer
time periods). The reason is that a faster reduction might be difficult to achieve given the
inertia in the energy production system: electrical power plants, for instance, have a technical
lifetime of 30 years or more. Fast reduction rates would require early replacement of existing
fossil-fuel-based capital stock, which may be associated with large costs. A maximum rate of
2%/year is hardly exceeded for the majority of the post-SRES mitigation scenarios, apart
from some lower stabilization scenarios (Swart et al., 2002; Eickhout et al., 2003;
Nakicenovic and Riahi, 2003; Azar et al., 2004; Hare and Meinshausen, 2004). As a result of
this assumed condition the departure from baseline emissions, reductions from the baseline
takes place relatively early, and global emissions peak around 2015-2020.
Figure 7. Global emissions relative to 1990 excluding (a) and including (b) LUCF CO2
emissions for the stabilization pathways at 550, 500, 450 and 400 ppm CO2-equivalent
concentrations for the three scenarios (CPI, CPI+tech and IMA-B1).
For all stabilization pathways, the global reduction rates remain below 2.5%/year for the
whole scenario period, except for the pathways at 400 ppm CO2-eq., with maximum
reduction rates of 2.5-3%/year over 20 years. Chapter 6 discusses the impact of a delay in the
peaking of the global emissions on the final reduction rates.
As previously mentioned, all mitigation pathways assumed either the CPI LUCF CO2
baseline emissions or those of the IMAGE B1 baseline. Thus, we left unchanged these
baseline LUCF CO2 emissions, based on a detailed calculation of landuse changes on the
basis of regional consumption, production and trading of food, animal feed, fodder, grass and
timber, with consideration of local climatic and terrain properties (IMAGE-team, 2001) (see
Figure C.2, Appendix C).
Greenhouse gas emission reductions excluding and including LUCF CO2 emissions are
analyzed here. Given the assumption of these static LUCF scenarios with decreasing
emissions, the quantified reduction requirements obviously differ, depending on whether the
reduction requirements refer to all greenhouse gas emissions including LUCF CO2 or Kyoto
gas emissions (excl. LUCF CO2). In general, emission pathways for the CPI+tech and B1
baselines have slightly higher greenhouse gas emissions (excl. LUCF CO2) compared to the
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pathways under the CPI baseline for the same concentration target, because the LUCF CO2
emissions for the CPI+tech and B1 scenario are assumed to be lower (see Figure C.2).
By 2050, global greenhouse gas emissions (excl. LUCF CO2) will have to be near 40-45%
below 1990 levels for stabilization at 40 ppm CO2-eq. For higher stabilization levels, e.g.
450 ppm CO2-eq. stabilization, greenhouse gas emissions (excl. LUCF CO2) may be higher,
namely 15-25% below 1990 levels (Table 1). For the CPI+tech scenario, the reductions for
400 ppm (450 ppm) CO2-eq. are 50% (30%) in 2050 compared to 1990 levels. However, if
LUCF CO2 emissions do not decrease as rapidly as assumed here, but continue at presently
high levels, an additional reduction of Kyoto-gas emissions (excl. LUCF CO2) by around
10% are required up to 2050.
Global greenhouse gas emissions (incl. LUCF CO2) will have to decrease to 5% to 10%
below 1990 levels by 2050 for stabilization at 550 ppm CO2-eq. For stabilization at 500 ppm
CO2-eq., global Kyoto-gas emissions would need to be 15 to 25% below 1990 levels in 2050.
The reduction requirements now become as high as 50-55% and 30-40% below 1990 levels
in 2050 to reach the 400 ppm and 450 ppm CO2-eq. target, respectively (instead of 40-45%
and 15-25%, respectively) (see Figure 7b). These reductions are about 10-15% higher than
the reductions of the Kyoto gas emissions excluding LUCF CO2.
In general, when we compare the reductions for the different concentration levels, we find
that about 15-20% additional reductions by 2050 are needed for every 50 ppm lower
stabilization level. We also see that higher near-term emissions need to be compensated by
lower future emissions (compare CPI and CPI+tech with B1 of the 500 ppm level, for
example).
Appendix C shows the emission pathways of the individual greenhouse gases for the
stabilization pathways.
Table 1: Change of global GHG emissions (incl. and excl. LUCF CO2 emissions) compared
to 1990 levels (in %) (rounded to the nearest multiple of 5%).
2020
Incl. LUCF CO2
B1
CPI
CPI+tech
B1
CPI
CPI+tech
B1
CPI
CPI+tech
B1
Excl. LUCF CO2
CPI+tech
400ppm
450ppm
500ppm
550ppm
Incl. LUCF CO2
CPI
Baseline
2050
Excl. LUCF CO2
−
−
35
35
15
25
30
30
15
20
25
25
−
−
35
40
20
30
35
40
20
30
35
35
−
−
-25
-10
-55
-40
-25
-10
-50
-30
-15
-5
−
−
-20
0
-45
-25
-5
10
-40
-15
0
10
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4 Global emission abatement costs
In its Third Assessment Report (TAR), the IPCC presents estimates for macro-economic
costs (i.e. loss in GDP growth) of stabilization of the CO2 concentration. For stabilization of
the CO2 concentration at 450 ppm (comparable to 500-525 ppm CO2-eq.), GDP reductions
for 2050 have to be 1.0-4.0% (see Figure 8.18 in Hourcade and Shukla (2001).The range is
primarily derived from the assumption of different baseline scenarios (B1 to A1FI,
respectively). These are global estimates, with some sectors and also regions (e.g. the oilexporting regions) being likely to be more severely affected (e.g., van Vuuren et al., 2003).
These GDP costs have to be seen in perspective though. On the one hand, such long-term
GDP abatement costs are approximately equivalent to a delay of only a couple of years with
respect to a point in time, while the world might experience a twenty-fold increase in its
GDP around 2100 compared to present levels (Azar and Schneider, 2002; 2003).
Furthermore, the climate damage avoided and ancillary benefits are not included in such cost
estimates, although they might be comparable in scale.
Here, we present some results of the global abatement costs as a percentage of world GDP
for the different CO2-equivalent concentration levels. Before presenting the costs, it should
be noted that these costs only represent the direct-cost effects based on MAC curves but not
the various linkages and rebound effects via the economy or impacts of carbon leakage. In
other words, there is no direct link with macro-economic indicators such as GDP losses or
other measures of income of utility loss. The cost figures are also very dependent on our
assumptions about abatement potentials and reduction costs for all greenhouse gases. For a
further discussions on the limitations, but also the strengths of this cost methodology we
refer to den Elzen et al. (2005b).
Global costs increase for lower stabilization levels. The emission pathways show an increase
of the costs up to 2050, and then a general decrease as GDP growth outstrips the growth in
calculated abatement costs for most of the pathways (Figure 8).
2.0
2.0
a
550
1.5
500
1.5
1.0
1.0
0.5
0.5
0.0
2000 2025 2050 2075 2100
2.0
CPI
450
0.0
2000 2025 2050 2075 2100
2.0
CPI t ech
1.5
1.0
b
B1
c
d
400
1.5
1.0
0.5
0.5
0.0
2000 2025 2050 2075 2100
0.0
2000 2025 2050 2075 2100
Figure 8. Global abatement costs as % of GDP for the stabilization pathways at
(a) 550 ppm, (b) 500 ppm, (c) 450 ppm and (d) 400 ppm CO2-equivalent concentrations for
the three baseline scenarios (CPI, CPI+tech and IMA-B1).
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The Figure also shows that the global abatement costs are even more influenced by the
baseline emissions and the assumed improvements in technical change of the abatement
potentials and costs than the final concentration stabilization level, as was also concluded by
the IPCC. More specifically, the baseline emissions directly determine the reductions that are
required to reach the emission profile for stabilization. The economic assumptions also
obviously influence the relative cost measures such as GDP losses or abatement costs such as
percentage of GDP.
Another crucial uncertainty is the rate at which the abatement costs for CO2 and non-CO2
emission reductions develop in time (compare the CPI and CPI+tech baseline scenario – see
chapter 2). Given these uncertainties and limitations (mainly that ancillary benefits are not
included and climate damage avoided), the results should be taken as qualitatively indicative,
but not as quantitatively robust.
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5 The regional emission implications
This chapter analyses the implications of the global emission pathways for the regional
emission allowances for two international regimes for differentiating future (post-2012)
commitments: the Multi-Stage and Contraction & Convergence approach using the FAIR 2.0
model. These regimes are outlined below:
(1) The Multi-Stage approach is an incremental but rule-based approach, which assumes a
gradual increase in the number of Annex I Parties involved who adopting binding quantified
emission intensity targets or absolute reduction objectives, whether absolute or dynamic
(Berk and den Elzen, 2001; den Elzen, 2002). More specifically, the Multi-Stage approach
here is based on three consecutive stages for the commitments of non-Annex I regions
beyond 2012: i.e. Stage 1 – no commitment (baseline emissions), Stage 2 – emission
limitation targets (intensity targets) and Stage 3 – absolute reduction targets. Participation
thresholds are used for the transition from Stage 1 to 2, and from Stage 2 to 3 (see also den
Elzen et al., 2005a; 2005b). Participation thresholds are based on a Capability–Responsibility
index (e.g., Criqui and Kouvaritakis, 2000), and is defined as the sum of per capita GDP
income (in PPP€1000 per capita18), which relates to the capability to act, and of per capita
CO2-equivalent emissions (in tCO2 per capita), reflecting the responsibility in climate
change. Current (2000) index values vary widely between countries, ranging from below 2
for Eastern and Western Africa, 4 for India and 8 for China, 11 for Central and South
America, 12 for the Middle-East to as high as 29 for Europe and 54 for the USA.19
For Stage 2, the intensity improvement targets are defined as a linear function of per capita
income level, and thereby relax the emission limitations for the low-income, non-Annex I
regions. A maximum rate is adopted to avoid de-carbonization rates that would outpace those
of economic growth, here this is 3% at 50% of 1995 Annex I per capita GDP income (in
PPP€). In Stage 3, the total reduction effort to achieve the global emissions profile is shared
by all participating regions on the basis of a burden-sharing key (here, per capita emissions).
All Annex I regions (including the USA)20 are assumed to have reached Stage 3 after 2012.
(2) The Contraction & Convergence approach assumes universal participation and defines
emission allowances on the basis of convergence of per capita emission allowances (starting
after 2012) in 2050 for all countries under a contracting global emissions profile (Meyer,
2000).
The Contraction & Convergence approach is the most widely known, transparent and
comprehensive approach, and has much appeal in the developing world. The Multi-Stage
approach is selected here, as this approach best satisfies the various types of criteria
18
GDP levels of different countries are normally compared on the basis of conversion to a common
currency using Market Exchange Rates (MER). However, this is known to underestimate the real income levels
of low-income countries. Therefore, an alternative conversion has been developed on the basis of purchasing
power parity (PPP). Here, we have usually used PPP-based GDP estimates; however, MER-based estimates for
comparison were used where required.
19
The CR values for 2025 under the CPI baseline scenario for the non-Annex I regions are: 5 for Eastern
and Western Africa, 10 for India and 18 for China, 17 for Central and South America and 18 for the Middle
East (see for more details den Elzen et al., 2005a).
20
Obviously, there is no certainty that this will happen. However, it is hard to conceive of any global
climate regime that is compatible with stabilising GHG concentrations at 550 ppmv equivalent or lower if the
USA decides against joining the international effort to reduce emissions, even after 2012. This is analysed in
Chapter 6.
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(environmental, political, economic, technical, institutional) in the multi-criteria evaluation of
various approaches by Höhne et al. (2003) and den Elzen et al. (2003).
The basic methodology of the analysis consists of two steps:
1. starting with a baseline emissions scenario and a global emission pathway; defining
the global emission reduction objective;
2. calculating regional emission reduction targets for the two regimes within the context
of this global reduction objective.
The reference cases of the Multi-Stage and Contraction & Convergence for the 550 ppm
pathway are described in detail in den Elzen et al. (2005a; 2005b), and correspond to the
cases in the EU research project ‘Greenhouse gas reduction pathways in the UNFCC postKyoto process up to 2025’ (Criqui et al., 2003). As for the 550 ppm concentration pathway,
the Multi-Stage parameters are chosen such that the Annex I countries take the lead in the
reduction efforts compared to the baselines, followed by the middle- and high-income
non-Annex I regions and, finally, the low-income non-Annex I regions (Table 2).
Table 2: The reference cases of the Multi-Stage and Contraction & Convergence regimes for
the four CO2 equivalence stabilization pathways
Multi-Stage
Contraction &
Convergence
a
Parameters
• First participation
threshold for stage 2
400 ppm
CRa index =
2
450 ppm
CR index =
3
500 ppm
CR index =
4
550 ppm
CR index =
5
• Second participation CR index =
9
threshold for stage 3
CR index =
10
CR index =
11
CR index =
12
• Convergence year
2050
2050
2050
2050
CR = Capability–Responsibility
The Annex I commitments need to be intensified in all cases after 2012 (see Figures 9 and
10). In 2020, Annex I Kyoto-gas emissions21 need to be reduced by approximately 25-30%
in comparison with 1990 levels for 400 ppm, and approximately 15-20% for 450ppm
stabilization. The reductions compared to the CPI baseline are about 10-15% higher. In 2050,
the reductions below 1990 levels stand at about 90% (400 ppm) and 80% (450 ppm),
respectively.
Most non-Annex I regions will need to reduce their emissions by 2020 compared to baseline
levels, but emissions can increase compared to 1990 under all regimes analysed. For nonAnnex I regions, the results are generally more differentiated for the various commitment
schemes and time horizons (2020 versus 2050) than for Annex I regions. For the low-income
regions (Southern Asia (India), Western Africa and Eastern Africa (not shown)), the
reductions in 2020 are less than 10% compared to the baseline level for all stabilization
pathways. Emission allowances for these regions may even exceed baseline emissions for
these low-income regions under 500 ppm and 550 ppm CO2-eq. for the Contraction &
Convergence regime. For the middle- and high-income non-Annex I regions, the reductions
compared to the baseline emissions in 2020 are below the reductions for the Annex I regions,
about 20-25% and 30-40% for 450 and 400 ppm, respectively, but increase to about 70% and
21
Kyoto gas emissions are here defined as including fossil CO2, CH4, N2O, HFCs, PFCs, and SF6
emissions; GWP-weighted; excluding LUCF CO2 emissions.
Netherlands Environmental Assessment Agency
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80% for 450 and 400 ppm, respectively by 2050. These reductions are still less than the
Annex I reductions compared to their baseline emissions.
60.
%-change compared to 1990-level in 2020
200
%-change compared to 1990-level in 2020
a
b
45
150
30
CPI+tech
100
15
50
0
0
-15
-50
-30
-100
-45
Global
Annex
I Canada
Enlarged
FSU
%-change
compared
to 1990-level
in 2050
& USA
EU
Oceania
Japan
c
NonLatin
Africa
ME &
South
%-change compared to 1990-level in 2050
Annex I America
Turkey
Asia
500
d
SE &
E.Asia
400
CPI+tech
60
45
30
15
0
-15
-30
-45
-60
-75
-90
400ppm
450ppm
500ppm
550ppm
Baseline
300
200
100
0
-100
Global
Annex I Canada Enlarged
& USA
EU
FSU
Oceania
Japan
NonLatin
Africa
Annex I America
ME &
Turkey
South
Asia
SE &
E.Asia
Figure 9. Change in Kyoto-gas emission allowances (excluding LUCF CO2 emissions)
before emissions trading from 1990 to 2020 (upper) and 2050 (lower) for the Annex I
regions (a,c) and non-Annex I regions (b,d) under the Multi-Stage approach for the
stabilization pathways at 550, 500, 450 and 400 ppm CO2-equivalent concentrations for the
CPI+tech scenario.
%-change compared to 1990-level in 2020
60
45
%-change compared to 1990-level in 2020
200
a
150
30
400ppm
450ppm
500ppm
550ppm
Baseline
CPI+tech
100
15
50
0
0
-15
-50
-30
-45
-100
Global Annex
I Canada
Enlarged
FSU
%-change
compared
to 1990-level
in 2050
& USA
EU
Oceania
Japan
c
Non-compared
Latin to Af
rica
ME
&
South
%-change
1990-level
in 2050
Turkey
Asia
500 Annex I A merica
400
d
SE &
E.A sia
CPI+tech
60
45
30
15
0
-15
-30
-45
-60
-75
-90
b
300
200
100
0
-100
Global
Canada
& USA
FSU
Japan
NonLatin
A frica
A nnex I America
ME &
Turkey
South
Asia
Figure 10. Same as Figure 9, but now under the Contraction & Convergence regime.
SE &
E.A sia
Netherlands Environmental Assessment Agency
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Stabilization levels versus regime – In comparing Figures 9 and 10 we also see that the
average emission reductions over the two regimes for each region are more influenced by the
assumed stabilization pathways than by the regime options explored. In general, the MultiStage cases give quite similar results to the Contraction & Convergence case. The main
difference is the somewhat higher reductions for the Annex I and middle- and high-income
non-Annex I regions by 2020 under Multi-Stage, as these regions have to compensate the
surplus emissions (hot air) of the low-income regions. Similar to the Contraction &
Convergence case, the Multi-Stage case leads, to some convergence in the per capita
emissions by around 2050 too as a result of the applied burden-sharing key based on per
capita emissions. This is not a full convergence, though, and therefore, the reductions of the
Annex I regions are, in the long-term (2050), somewhat less under the Multi-Stage regime.
Netherlands Environmental Assessment Agency
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6 The impact of further delay in emission reductions
6.1 Delay in peaking of global emissions
To underscore the importance of early action, an analysis was performed, in which the date
of global emissions peaking is delayed. Figure 11 shows the emissions of the Kyoto gases
(including LUCF CO2 emissions) applied to the different delayed simulations for
stabilization at 400 ppm and 450 ppm CO2-eq. The default and the sensitivity pathways
imply by construction the same risk of overshooting 2°C.22 Specifically, emissions peak
around 2015 under the default pathway, and at a 5% higher peak at 2015 for the first
sensitivity pathway and around 2020 for the second delayed pathway. For 450 ppm,
emissions peak at 2015 for default pathway ‘0’ and pathway ‘1’ and 2020 for pathways ‘2’,
and ‘3’, with pathways ‘1’ and ‘3’ assuming a slower decrease after peaking compared to ‘0’
and ‘4’ (Figure 11). Absolute levels turn out lower than the default pathway around 2040 in
order to compensate for the initially higher emissions. Not only will absolute emission levels
beyond 2050 have to be lower under the delayed emission pathways, but the required
emission reduction rates around 2025 will also have to be steeper. If we delay the peaking of
the global emissions until 2020, this needs to be compensated by steeper maximum reduction
rates hereafter, i.e. in the order of 5.4%/year for 400 ppm CO2-eq. and 3.9%/year for
450 ppm CO2-eq., for at least 20 years. Another five-year delay for the 450 ppm target also
leads to maximum reduction rates in the order of 5%/year.
Figure 11. The impact of delaying action for greenhouse gas emission reductions (incl.
LUCF CO2) for the stabilization pathways at (a) 450 ppm and (b) 400 ppm CO2-equivalent
concentrations for the baseline scenario IMA-B1. The delayed paths (1,2,3) meet the
condition that the risk of overshooting 2°C is not increased compared to the default path (0).
Concluding, global emissions will have to peak in 10 to 15 years to limit the risk of
overshooting 2°C to reasonable levels. The consequences of delay are lower absolute
emissions after around 2050, and steeper maximal reduction rates from as early as 2020 and
2025.
22
Practically speaking, the condition imposed on the delayed emission pathways was that they would have
to peak at the same temperature level as in the default scenario.
Netherlands Environmental Assessment Agency
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6.2 The impact of a further delay in USA involvement in emission reductions
A special case of a further delay in emission reductions is a further delay in the USA
involvement in the emission reductions. In the previous calculations of future commitments,
we assumed that the USA would participate in the reductions from 2012 onwards, and thus
re-enters in the post-2012 regime for differentiation of future commitments. However, a
change in the USA position under the Bush administration is very unlikely. A change of
USA involvement seems possible for a subsequent administration, at the earliest after the
next presidential elections (2008), though. Even then, the timing of emission reductions to be
expected by the USA is very uncertain. Here, we want to explore two possible scenarios,
besides the re-entrance case of the USA from 2012 onwards. The first scenario assumes that
the USA does not take on commitments for at least the coming two decades after 2012. A
second scenario assumes the USA adopts the target proposed in the Senate Bill 139 (S.139),
the Climate Stewardship Act of 2003. This legislation, proposed by USA Senators McCain
and Lieberman, is the most detailed effort to date to design an economy-wide cap-and-trade
system for USA greenhouse gas emissions reductions. The Act caps sectors at their 2000
emissions in Phase I of the program, running from 2010 to 2015, and then to their 1990
emissions for Phase II starting 2016. The program would apply to greenhouse gas emissions
from major sectors – electric utilities, transportation, and industry – covering roughly 80% of
USA emissions. Several economic and policy analyses have been performed in the past (e.g.,
EIA, 2003; Paltsev et al., 2003; Berk and den Elzen, 2004). Here, we will also analyse the
impact of the re-entrance of the USA under the Climate Stewardship Act. In our calculations
we assume the same trajectory of the total greenhouse gas emissions as estimated in EIA
(2003), i.e. a return of USA total greenhouse gas emissions to 2000 levels by 2025, with the
gradual decline in USA total emissions starting in 2012.
Here, we want to explore two possible cases, besides the re-entrance case of the USA from
2012 (default Case 0) onwards:
• Case 1 (‘USA and non-Annex I no action’): the USA (and Australia) just follow their
baseline emissions for at least the following two decades. No non-Annex I Parties
take on commitments beyond 2012.
• Case 2 (‘USA Lieberman-McCain and advanced non-Annex I action’): the USA
follows our implementation of the Lieberman-McCain Climate Stewardship Act of
2003 (S.139)23, with the USA total greenhouse gas emissions reaching 2000 levels by
2025. Australia and the non-Annex I regions with a CR-index above 12 (advanced or
middle- and high- income regions) adopt income-dependent intensity targets after
2012 (Stage 2 of Multi-Stage). The same holds for the USA after 2025.
For both cases the EU and the rest of the Annex I share the total reductions needed to achieve
the global emission pathway for the stabilization pathways at 550, 500, 450 and 400 ppm
CO2-equivalent concentrations, as summarized in Table 3 and illustrated in Figure 12. Here,
also the results of Case 0, US re-entrance by 2012, are given for comparison. The analysis
uses the emission pathways under the CPI+tech scenario, which basically employs the CPI as
baseline emission scenario (see Chapter 2), as this is a medium-level scenario. The reductions
presented in this section are baseline-dependent, and will be less under the B1 scenario.
For Case 1, the EU and the rest of Annex I have to reduce emissions by more than 55% for
550 ppm in 2020 compared to 1990 levels and to more than 95% for 400 ppm. By the year
2030, their emissions reach zero levels. Figure 12 shows the world emissions to outgrow the
emission pathway of 400 and 550 ppm CO2-eq. by 2025 and 2030, respectively.
23
See: http://www.climatenetwork.org/csa.htm, for links to useful resources about the bill.
Netherlands Environmental Assessment Agency
page 28 of 44
For Case 2, the EU and the rest of Annex I need to reduce their emissions by 35-40% in 2020
for the 500 and 550 ppm targets, whereas for 400 and 450 ppm the reductions are more than
55% (450 ppm) to 80% (400 ppm). By the year 2030, the zero emission levels are reached
for 400 and 450 ppm, and reductions are more than 50% for the higher concentration levels.
Case 0: US re-entrance 2012, non-Annex I gradually participation
GtC O2/yr
70
GtC O2/yr
CO2-eq. emissions
60
EU and rest A nnex I
USA & Oceania
50
non-A nnex I
a
400
30
20
20
10
10
2020
2030
2040
2050
time (years)
0
1990
C PI+tech
30
2010
550
50
40
2000
b
60
40
0
1990
CO2-eq. emissions
70
2000
2010
2020
2030
2040
2050
time (years)
Case 1: no action USA and non-Annex I
GtC O2/yr
GtCO2/yr
CO2-eq. emissions
70
c
60
400
40
40
30
30
20
20
10
10
2010
2020
2030
2040
2050
time (years)
0
1990
550
C PI+tech
50
2000
d
60
50
0
1990
CO2-eq. emissions
70
2000
2010
2020
2030
2040
2050
time (years)
Case 2: USA Lieberman and advanced non-Annex I action I
GtC O2/yr
GtCO2/yr
CO2-eq. emissions
70
e
60
400
40
40
30
30
20
20
10
10
2010
2020
2030
2040
2050
time (years)
0
1990
550
CPI+tech
50
2000
f
60
50
0
1990
CO2-eq. emissions
70
2000
2010
2020
2030
2040
2050
time (years)
Figure 12. The impact of 2012 re-entrance of the USA (Case 0) versus no or partial
involvement of the USA (Case 1 and 2) in the emission reductions for the stabilization
pathways (excluding LUCF CO2) at 400 ppm (a,c,e) and 550 ppm (b,d,f). The point where
the stacked emissions surpass the stabilization pathways (black bold line) indicates the date
on which world emissions outgrow the emission pathway.
Netherlands Environmental Assessment Agency
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Table 3: The total emission reduction targets below 1990 levels (in %) for the enlarged EU
for the four stabilization pathways for the default emission pathways for the CPI+tech
scenario. Note: the rest of the Annex I Parties (Canada, FSU and Japan) show similar reductions.
Stabilization level
2020
-29
Case 0: Default (all Parties
400ppm
-20
participate gradually)
450ppm
-16
500ppm
-15
550ppm
Case 1: USA and non400ppm
X
-79
Annex I no action
450ppm
-61
500ppm
-57
550ppm
-82
Case 2: USA Lieberman400ppm
-54
McCain and advanced
450ppm
-38
non-Annex I action
500ppm
-34
550ppm
X= reductions of more than 95% (almost zero emission allowances).
2025
-45
-32
-23
-20
X
X
X
-92
X
X
-58
-49
2030
-59
-45
-30
-26
X
X
X
X
X
X
-82
-66
This analysis clearly shows that partial or no involvement of the USA in the reductions in the
coming two decades will lead to ‘unrealistic’ fast and deep emission reduction commitments
for the EU and the rest of Annex I in order to achieve the low stabilization levels. Such deep
reductions seem politically, technically and economically unfeasible. In order to keep the
options open for achieving the 2°C target with a reasonable certainty, it is necessary to have
much more substantial USA involvement in the reductions than formulated in the McCainLieberman Bill. The more advanced non-Annex I countries (big emitters, such as China) will
also need to take on reduction commitments before 2025.
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7 Conclusions
This study describes a method to derive multi-gas pathways that closely reflects the existing
international framework of pre-set caps on aggregated emissions and individual costoptimising actors. Thus, cost-optimal mixes of greenhouse gases reductions are derived for a
given global emission pathway. The presented emission pathways stabilize CO2-equivalent
concentration at 550, 500, 450 and 400 ppm. Here, we follow a ‘peaking strategy’, allowing
concentrations to peak then decrease before stabilising, i.e. going up to 480-500 ppm CO2equivalent before going down to levels such as 400 or 450 ppm equivalent later on.
As previously shown (see e.g. Hare and Meinshausen, 2004) emission pathway leading to a
550ppm CO2-equivalent stabilization is unlikely to meet the climate target of limiting global
mean temperature rise to 2°C above pre-industrial levels (EU 2°C target). In order to achieve
such the EU 2°C target with a probability of more than 85% (60%) (assuming the
probabilistic density function of Wigley and Raper, 2001), greenhouse gas concentrations
need to be stabilized below 450 (400) ppm CO2-equivalent or lower. This, in turn, requires
global emissions to peak around 2015 in order to avoid global reduction rates exceeding
more than 2.5%/year, followed by substantial overall reductions by as much as 40 to 45%
(15 to 25%) in 2050 compared to 1990 levels, excluding LUCF CO2 emissions. The
reduction requirements become as high as 50 to 55% (30 to 40%) below 1990 levels in 2050
for all greenhouse gas emissions, including LUCF CO2.
The analysis here shows that abatement costs will depend heavily on the emission growth in
the baseline scenario, as well as on further developments of the abatement potential and
reduction costs for all greenhouse gases in the future. Along with this, early action to achieve
the benefits from learning and induced technological progress, as well as the removal of
implementation barriers, are likely to highly influence the costs of mitigation efforts to
achieve certain climate targets. The allowable delay in the peaking emissions is limited, less
than 5-10 years delay. In order to avoid climate impacts that are associated with a global
mean temperature rise of 2°C and more, the global emissions within the next two decades
will need to be peaked.
The analysis of the regional emission implications of two post-2012 regimes for
differentiating commitments, i.e. a convergence and multi-stage regime, for the default
emission pathways shows that Annex I emissions in 2020 will need to be reduced by about
15-30% below 1990 levels for 400-450 ppm CO2-eq. To realize these concentration levels
major non-Annex I countries will have to participate in the reductions within the near future
(next two decades).
The analysis of delaying global action shows that the emission reduction implications of a
further delay in peaking of just five years could be significant, resulting in much steeper
reductions from as early as 2020 and 2025. A delay in action to reduce emissions up to 20202025 leads to a doubling of the maximum rates of emission reductions to about 5%/year, in
order to meet concentration levels of 450 ppm CO2-equivalent or lower. Such high reduction
rates are difficult to achieve, given the inertia in the energy production system, and will lead
to large costs that would be associated with the premature retirement of existing fossil-fuelbased capital stock. Thus, in order to avoid climate impacts that are associated with a global
mean temperature rise of 2°C and more, global emissions will need to peak around 2015. We
also analysed a further delay in USA involvement in emission reductions. In order to keep
the option open of stabilising concentrations at 400 and 450 ppm CO2-equivalent, the
Netherlands Environmental Assessment Agency
page 31 of 44
participation of the USA and the advanced non-Annex I countries in the reduction
commitments well before 2025 is needed. Otherwise, ‘unrealistic’ rapid and sharp emission
reduction requirements for the EU and the rest of Annex I will be the result if the probability
of overshooting 2°C shall be limited to reasonable levels.
Netherlands Environmental Assessment Agency
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References
ACIA, 2004. Impacts of a Warming Arctic - Arctic Climate Impact Assessment.
Allen, M. R. and Lord, R., 2004. The blame game - who will pay for the damaging
consequences of climate change? Nature, 432: 2 December 2004.
Azar, C., Linddgren, K., Larson, E. and Möllersten, K., 2004. Carbon capture and storage
from fossil fuels and biomass - Costs and potential role in stabilizing the atmosphere.
Climatic Change (submitted).
Azar, C. and Schneider, S. H., 2002. Are the economic costs of stabilising the atmosphere
prohibitive? Ecological Economics, 42(1-2): 73-80.
Azar, C. and Schneider, S.H., 2003. Are the economic costs of (non-)stabilizing the
atmosphere prohibitive? A response to Gerlagh and Papyrakis. Ecological
Economics, 46(3): 329-332.
Berk, M.M. and den Elzen, M.G.J., 2001. Options for differentiation of future commitments
in climate policy: how to realise timely participation to meet stringent climate goals?
Climate Policy, 1(4): 465-480.
Berk, M.M. and Elzen, M.G.J. den, 2004. What if the Russians don't ratify? RIVM report
728001028, National Institute for Public Health and the Environment, Bilthoven, the
Netherlands (www.mnp.nl/ieweb).
Criqui, P., Kitous, A., Berk, M.M., den Elzen, M.G.J., Eickhout, B., Lucas, P., van Vuuren,
D.P., Kouvaritakis, N. and Vanregemorter, D., 2003. Greenhouse gas reduction
pathways in the UNFCCC Process up to 2025 - Technical Report. B43040/2001/325703/MAR/E.1 for the DG Environment, CNRS-IEPE, Grenoble,
France.
Criqui, P. and Kouvaritakis, N., 2000. World energy projections to 2030. International
Journal of Global Energy Issues, 14(1-4): 116-136.
Cubasch, U., Meehl, G. A., Boer, G. J., Stouffer, R. J., Dix, M., Noda, A., Senior, C. A.,
Raper, S. and Yap, K.S., 2001. Projections of Future Climate Change. In: J.T.
Houghton et al. (Editors), Climate Change 2001: The Scientific Basis. Cambridge
University Press, Cambridge, UK.
de Vries, H.J.M., van Vuuren, D.P., den Elzen, M.G.J. and Janssen, M.A., 2002. The Targets
Image Energy model regional (TIMER) - Technical documentation. RIVM report
461502024, National Institute for Public Health and the Environment, Bilthoven, the
Netherlands.
DeAngelo, B. J., DelaChesnaye, F. C., Beach, R. H., Sommer, A. and Murray, B. C., 2004.
Methane and nitrous oxide mitigation in agriculture. Energy Journal (in press).
Delhotal, K. C., DelaChesnaye, F. C., Gardiner, A., Bates, J. and Sankovski, A., 2004.
Mitigation of methan and nitrous oxide emissions from waste, energy and industry.
Energy Journal (in press).
den Elzen, M.G.J., 2002. Exploring climate regimes for differentiation of future
commitments to stabilise greenhouse gas concentrations. Integrated Assessment,
3(4): 343-359.
den Elzen, M.G.J., Berk, M.M., Lucas, P., Criqui, C. and Kitous, A., 2005a. Multi-Stage: a
rule-based evolution of future commitments under the Climate Change Convention.
International Environmental Agreements (in press).
den Elzen, M.G.J., Berk, M.M., Lucas, P., Eickhout, B. and Vuuren, D.P. van, 2003.
Exploring climate regimes for differentiation of commitments to achieve the EU
climate target. RIVM-report 728001023, National Institute for Public Health and the
Environment, Bilthoven, the Netherlands (www.mnp.nl/ieweb).
Netherlands Environmental Assessment Agency
page 33 of 44
den Elzen, M.G.J. and Lucas, P., 2003. FAIR 2.0: a decision-support model to assess the
environmental and economic consequences of future climate regimes,
www.mnp.nl/fair. RIVM-report 550015001, National Institute for Public Health and
the Environment, Bilthoven, the Netherlands (www.mnp.nl/ieweb).
den Elzen, M.G.J. and Lucas, P., 2005. The FAIR model: a tool to analyse environmental
and costs implications of climate regimes. Environmental Modeling & Assessment,
accepted for publication.
den Elzen, M.G.J., Lucas, P. and van Vuuren, D.P., 2005b. Abatement costs of post-Kyoto
climate regimes. Energy Policy, 33(16): pp. 2138-2151.
EIA, 2003. Analysis of S.139, the Climate Stewardship Act of 2003: Highlights and
Summary. Energy Information Administration Report SR/OIAF/2003-02/S, Energy
Information Administration, Washington, DC.
Eickhout, B., den Elzen, M.G.J. and van Vuuren, D.P., 2003. Multi-gas emission profiles for
stabilising greenhouse gas concentrations. RIVM-report 728001026, National
Institute for Public Health and the Environment, Bilthoven, the Netherlands
(www.mnp.nl/ieweb).
Enting, I.G., Wigley, T.M.L. and Heimann, M., 1994. Future emissions and concentrations
of carbon dioxide, Mordialloc, Australia.
European-Council, 1996. Communication on Community Strategy on Climate Change,
Council Conclusions, European Council, Brussels.
European-Council, 2005. Presidency conclusions, European Council, Brussels.
Folland, C. K., Rayner, N. A., Brown, S. J., Smith, T. M., Shen, S. S. P., Parker, D. E.,
Macadam, I., Jones, P. D., Jones, R. N., Nicholls, N. and Sexton, D. M. H., 2001.
Global temperature change and its uncertainties since 1861. Geophysical Research
Letters, 28(13): 2621-2624.
Fuglestvedt, J.S., Berntsen, T.K., Godal, O., Sausen, R., Shine, K.O. and Skodvin, T., 2003.
Assessing metrics of climate change - current methods and future possibilities.
Climatic change, 58: 267-331.
Graus, W., Harmelink , M. and Hendriks, C., 2004. Marginal GHG-Abatement curves for
agriculture, Ecofys, Utrecht, the Netherlands.
Graveland, C., Bouwman, A.F., de Vries, H.J.M., Eickhout, B. and Strengers, B.J., 2002.
Projections of multi-gas emissions and carbon sinks, and marginal abatement cost
functions modelling for land-use related sources. RIVM-report 461502026, National
Institute for Public Health and the Environment, Bilthoven, the Netherlands
(www.mnp.nl/ieweb).
Gritsevskyi, A. and Nakicenovic, N., 2000. Modeling uncertainty of induced technological
change. Energy Policy, 28(13): 907-921.
Hansen, J., Sato, M., Ruedy, R., Lacis, A. and Oinas, V., 2000. Global warming in the
twenty-first century: An alternative scenario. Proceedings of the National Academy
of Sciences of the United States of America, 97(18): 9875-9880.
Hare, W.L., 2003. Assessment of Knowledge on Impacts of Climate Change – Contribution
to the Specification of Art. 2 of the UNFCCC, WBGU - German Advisory Council
on Global Change, Potsdam, Berlin.
Hare, W.L. and Meinshausen, M., 2004. How much warming are we committed to and how
much can be avoided?, Potsdam Institute for Climate Impact Research (PIK),
Potsdam, Germany.
Hayhoe, K., Jain, A., Pitcher, H., MacCracken, C., Gibbs, M., Wuebbles, D., Harvey, R. and
Kruger, D., 1999. Costs of multigreenhouse gas reduction targets for the USA.
Science, 286: 905-906.
Hitz, S. and Smith, J., 2004. Estimating global impacts from climate change. Global
Environmental Change Part A, 14(3): 201-218.
Netherlands Environmental Assessment Agency
page 34 of 44
Höhne, N., 2005. Impact of the Kyoto Protocol on Stabilization of Carbon Dioxide
Concentration, Scientific Symposium “Avoiding Dangerous Climate Change”, Met
Office, Exeter, United Kingdom.
Höhne, N., Galleguillos, C., Blok, K., Harnisch, J. and Phylipsen, D., 2003. Evolution of
commitments under the UNFCCC: Involving newly industrialized countries and
developing countries. Research-report 20141255, UBA-FB 000412, ECOFYS Gmbh,
Berlin.
Hourcade, J-C. and Shukla, P.R., 2001. Global, regional and national costs and ancillary
benefits of mitigation. In: B. Metz, Davidson, O., Swart, R., Pan, J. (Editor), Climate
Change 2001: Mitigation; Contribution of Working Group III to the Third
Assessment Report of the IPCC. Cambridge University Press, Cambridge, UK.
IMAGE-team, 2001. The IMAGE 2.2 implementation of the SRES scenarios. A
comprehensive analysis of emissions, climate change and impacts in the 21st century.
CD-ROM publication 481508018, Bilthoven, the Netherlands.
IPCC, 2001. Climate Change 2001: Mitigation. Cambridge University Press, Cambridge,
UK.
Joos, F., Plattner, G.-K., Stocker, T.F., Marchal, O. and Schmittner, A., 1999. Global
warming and marine carbon cycle feedbacks on future atmospheric CO2. Science,
284: 464-467.
Manne, A.S. and Richels, R.G., 2001. An alternative approach to establishing trade-offs
among greenhouse gases. Nature, 410: 675-677.
Meinshausen, M., 2005. On the Risk to Overshoot 2°C, Scientific Symposium “Avoiding
Dangerous Climate Change”, Met Office, Exeter, United Kingdom.
Meinshausen, M., Hare, W.L., Wigley, T.M.L., van Vuuren, D.P., den Elzen, M.G.J and
Swart, R., 2004. Multi-gas emission pathways to meet climate targets. Climatic
change (submitted).
Meyer, A., 2000. Contraction & Convergence. The global solution to climate change.
Schumacher Briefings, 5. Green Books, Bristol, UK.
Morita, T., Nakicenovic, N. and Robinson, John, 2000. Overview of mitigation scenarios for
global climate stabilization based on new IPCC emission scenarios (SRES).
Environmental Economics and Policy Studies, 3: 65-88.
Murphy, J.M., Sexton, D.M.H., Barnett, D.N., Jones, G.S., Webb, M.J., Collins, M. and
Stainforth, D.A, 2004. Quantification of modelling uncertainties in a large ensemble
of climate change simulations. Nature, 430: 768-772.
Nakicenovic, N. and Riahi, K., 2003. Model runs with MESSAGE in the Context of the
Further Development of the Kyoto-Protocol, WBGU - German Advisory Council on
Global Change, Berlin.
Paltsev, S., Reilly, J., Jacoby, H., Ellerman, A.D. and Tay, K.H., 2003. Emissions Trading to
Reduce Greenhouse Gas Emissions in the United States:The McCain-Lieberman
Proposal. Report No. 97, Massachusetts Institute of Technology, Cambridge, MA.
Raper, S. C. B. and Cubasch, U., 1996. Emulation of the results from a coupled general
circulation model using a simple climate model. Geophysical Research Letters,
23(10): 1107-1110.
Reilly, J., Prinn, R.G., Harnisch, J., Fitzmaurice, J., Jacoby, H., Kicklighter, D., Stone, P.,
Sokolov, A. and C., Wang., 1999. Multi-gas Assessment of the Kyoto Protocol.
Nature, 401(6753): 549-555.
Richels, R., Manne, A. and Wigley, T.M.L., 2004. Moving beyond concentrations: the
challenge of limiting temperature change. Working-Paper 04-11, AEI-Brookings
Joint Center for Regulatory Studies.
Schaefer, D. O., Godwin, D. and Harnisch, J., 2004. Estimating future emissions and
potential reductions of HFCs, PFCs and SF6. Energy Journal (in press).
Netherlands Environmental Assessment Agency
page 35 of 44
Schimel, D., Grubb, M., Joos, F., Kaufmann, R. , Moss, R. , Ogana, W. , Richels, R. and
Wigley, T. M. L, 1997. Stabilization of Atmospheric Greenhouse Gases: Physical,
Biological and Socio-Economic Implications. ISBN 92-9169-102-X, IPCC, Geneva.
Smith, J., Schnellnhubner, H.-J. and Mirza, M.Q.M., 2001. Vulnerability to climate change
and reasons for concern: a synthesis. In: J.J. McCarthy, O.F. Canziani, N.A. Leary,
D.J. Dokken and K.S. White (Editors), Climate Change 2001: Impacts, Adaptation,
and Vulnerability. Cambridge University Press, Cambridge, UK.
Stott, P.A., Stone, D.A. and Allen, M.R., 2004. Human contribution to the European
heatwave of 2003. Nature, 432: 610-614.
Swart, R., Berk, M., Janssen, M., Kreileman, E. and Leemans, R., 1998. The safe landing
analysis: risks and trade-offs in climate change. In: J. Alcamo, R. Leemans and E.
Kreileman (Editors), Global change scenarios of the 21st century. Results from the
IMAGE 2.1 model. Elseviers Science, London, pp. 193-218.
Swart, R., Mitchell, J., Morita, T. and Raper, S., 2002. Stabilisation scenarios for climate
impact assessment. Global Environmental Change, 12(3): 155-165.
Tol, R.S.J., 1999. The marginal Cost of greenhouse gas emissions. Energy Journal, 20(1):
61-81.
van Vuuren, D.P., de Vries, H.J.M., Eickhout, B. and Kram, T., 2004a. Responses to
Technology and Taxes in a Simulated World. Energy Economics, 26(579-601).
van Vuuren, D.P., den Elzen, M.G.J. and Berk, M.M., 2002. An evaluation of the level of
ambition and implications of the Bush Climate Change Initiative. Climate Policy, 2:
293-301.
van Vuuren, D.P., den Elzen, M.G.J., Berk, M.M., Lucas, P., Eickhout, B., Eerens, H. and
Oostenrijk, R, 2003. Regional costs and benefits of alternative post-Kyoto climate
regimes. RIVM-report 728001025, National Institute for Public Health and the
Environment, Bilthoven, the Netherlands.
van Vuuren, D.P., Eickhout, B., Lucas, P.L. and den Elzen, M.G.J., 2004b. Long-term multigas scenarios to stabilise radiative forcing - exploring costs and benefits within an
integrated assessment framework. Energy Journal (accepted).
van Vuuren, D.P., Weyant, J.P. and DelaChesnaye, F. C., 2005. Mult-gas scenarios to
stabilise radiative forcing. Energy Economics (submitted).
White-House, 2002. Executive Summary of Bush Climate Change Initiative.
Wigley, T. M. L, 2003. MAGICC/SCENGEN 4.1: Technical Manual, UCAR - Climate and
Global Dynamics Division, Boulder, CO.
Wigley, T. M. L. and Raper, S. C. B., 2001. Interpretation of high projections for globalmean warming. Science, 293(5529): 451-454.
Wigley, T. M. L. and Raper, S. C. B., 2002. Reasons for larger warming projections in the
IPCC Third Assessment Report. Journal of Climate, 15(20): 2945-2952.
Wigley, T. M. L., Richels, R. and Edmonds, J., submitted. Overshoot Pathways to CO2
stabilization in a multi-gas context. In: M.E. Schlesinger and J.P. Weyant (Editors),
Human Induced Climate Change: An Interdisciplinary Perspective. Cambridge
University Press, Cambridge, UK.
Wigley, T.M.L., Richels, R. and Edmonds, J.A., 1996. Economic and environmental choices
in the stabilisation of CO2 concentrations: choosing the ‘right’ emissions pathway.
Nature, 379: 240-243.
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Appendix A Description of the emission pathways
calculation
The driver parameterized global CO2-equivalent emission pathway is defined by sections of
constant yearly emission reductions (RI (initial 2010 value), RX, RY and RZ) and years (X1,
X2, Y3, Y4 and Z5) at which the reduction rates change, as indicated in Figure A.1. A
parameterization based on three periods of approximately constant reduction rates allows us
to match a stabilization profile reasonably well. Note that the effective emission reduction
rates will be different from the preset rates due to (a) smoothing of emissions profiles and (b)
lower bounds for some gases’ reductions, which affect lower emission pathways. These
lower bounds can result if a certain baseline and target emission path is chosen, which
emission gap is not fully covered by the chosen MAC curves. As well, the maximally
reducible amount of N2O and CH4 emissions after 2100 has been fixed at 75% of 2100
emissions, which can lead to a gap in preset and effective reduction paths after 2100 for
lower concentration pathways.
Figure A.1 The preset driver parameterized global CO2-equivalent emission pathway
(dotted), defined by sections of constant yearly emission reductions (RI (initial 2010 value),
RX, RY and RZ) and years at years (X1, X2, Y3, Y4 and Z5) at which the yearly reduction
changes. Effective reduction paths might differ (solid lines - see text). The plotted emission
pathways lead to a stabilization of radiative forcing. It is possible to create peaking emission
paths that would continue at Rx emission reduction rates.
The calculation of parameterized emission pathway aimed at concentration stabilization is
done in two steps:
1. First, calculate the parameter RX for a parameterized emission pathway (dotted line in
Figure A.1) leading to a concentration peaking in a certain year, using the iterative
procedure described in Chapter 2. Here, we need to make assumptions about the
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initial rate R0 and years X1, which are based on expert knowledge from existing
mitigation scenarios;24
2. Second, calculate the remaining parameters X2,Rz,Y1,Y2, Ry,Z1, Rz for a parameterized
emission pathway (solid dotted in Figure A.1), leading to a concentration
stabilization in a certain year.
24
Only for the emission pathway peaking at 480ppm CO2eq, do we also need to make assumptions about
the initial rate RY and years X2 and Y3, which are again based on information from the lower range of mitigation
scenarios in the literature.
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Appendix B Source of information on marginal
abatement costs
Table B.1: Source of information on marginal abatement costs for the default scenario
(adapted from van Vuuren et al., 2004b)
Emission category
(Non-CO2 gases)
Source of information on marginal
abatement costs
Reduction potential of
main sources (2010)
CH4 and N2O from
agricultural sources
DeAngelo et al. (2004) and Graus et
al. (2004) for development of
potential in 2010-2050 period
N2O soil: 7%
CH4 animals: 7%
*
CH4 rice: 20%
CH4 manure : 17%
CH4 and N2O emissions Delhotal et al. (2004)
from industrial and
energy-related sources
CH4 and N2O emissions This study
(no MAC curves
available)
Halocarbons
Schaefer et al. (2004); this study
Emission category
(CO2)
Source of information on marginal
abatement costs
CO2 from energy use
and production
Sinks
Time-dependent MACs of TIMER
(van Vuuren et al., 2004a) vvv
Based on IMAGE calculations
(Graveland et al., 2002)
Forest management
CH4 total : 65%
N2O process : 90-95%
Maximum reduction
(compared baseline) of
35% in 2040 x x
2010: around 40%
2100: 95% in 2100 vv
Reduction potential of
main sources
2010: Around 50%
2100: Around 80%
Potential increases to
400 MtC annually in
2050
Total amount of 135
MtC-eq. annually is
assumed
Assumed annual
increase of
potential
3.9% up to 2050
3.9% up to 2050
1.5% up to 2050
2.4% up to 2050;
0.4% 2050-2100 x
0.4% x
0.4% x
Assumed annual
increase of
potential
-x
-
Conservative assumptions based on
the extension of the Marrakesh
Accords as described in van Vuuren
et al. (2003).
*
In DeAngelo et al. (2004) a reduction of 38% is given. This number has been scaled down for 2010 on the
basis of Graus et al. (2004).
v
Here, van Vuuren et al. (2004b) assumed no reductions.
vv
Here, van Vuuren et al. assumed a 0.4% annual increase.
vvv
Here, Van Vuuren et al. assumed a time-dependent MACs iterating between FAIR and TIMER.
x
CPI + tech baseline scenario assumes a 2.0% annual increase of potential for non-CO2 emissions, and a 0.2%
additional technological improvement for CO2 emissions from energy use and production.
xx
CPI + tech baseline scenario assumes a 80% reduction in 2040.
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Appendix C Global greenhouse gas emissions of the
pathways presented
This appendix presents the emissions underlying the default pathways presented for
stabilization at 550, 450 and 400 ppm CO2-equivalent concentrations.
Figure C.1 Global fossil CO2 emissions. For comparison, the emission implications of the
IPCC-SRES non-mitigation scenarios (grey dotted lines) and a range of SRES mitigation
scenario (grey solid lines) are also plotted.
Figure C.2 Global landuse CO2, methane, nitrous oxide and halocarbon emissions. For
comparison, the emission implications of the IPCC-SRES non-mitigation scenarios (grey
dotted lines) and a range of SRES mitigation scenario (grey solid lines) are also plotted.
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Appendix D Comparison with IMAGE 2.2 multi-gas
emission pathways
This Appendix compares the emission pathways presented here with the two earlier IMAGE
multi-gas emission pathways, leading to a long-term stabilization at 550 and 650 ppm CO2eq. (hereafter referred to as the IMAGE S550e and S650e pathways) (Eickhout et al., 2003).
The IMAGE pathways have been used within the EU DG Environment project ‘Greenhouse
gas reduction pathways in the UNFCC post-Kyoto process up to 2025’ (see Criqui et al.,
2003). Table D.1 summarizes the differences between the two studies.
Table D.1 Differences between the earlier IMAGE multi-gas emission pathways (Eickhout et
al., 2003) and the emission pathways presented in this study
Differences
Definition profiles
CO2-eq. concentration
stabilization level
Final CO2 concentration
level
Eickhout et al. (2003)
This study
550 and 650 ppm in 2100 and 2150
400, 450, 500 and 550 ppm in 2250,
2250, 2200 and 2100
350-375, 400-425, 440-475 and
475-500 ppm CO2-only,
respectively.**
No overshoot for 550ppm CO2-eq.
Overshoot or peaking at 480, 500
and 525 ppm for stabilization
pathways at 400, 450 and 500
ppm, respectively.
Based on radiative forcing of all
greenhouse gases (incl. the CFCs,
HCFCs), tropospheric ozone and
aerosols (Schimel et al., 1997).
450 and 550 ppm CO2-only*
Including overshoot
No overshoot
Definition CO2-equivalent
concentration
Based on radiative forcing of the six
Kyoto greenhouse gases (CO2, CH4,
N2O, HFCs, PFCs, and SF6).
Baseline assumptions
LUCF CO2 emissions
CO2 emissions including CO2
fertilization effect.
Baseline scenario
CPI scenario
CO2 emissions not including CO2
fertilization effect (as feedbacks
included in used climate model
MAGICC)
CPI, CPI+tech and B1 scenario
Models used
Terrestrial carbon cycle
model
Oceanic carbon cycle model
Atmospheric chemistry
Climate model
Methodology
Methodology for the
calculation of emission
pathways
Geographical explicit carbon cycle
model (IMAGE 2.2)
ocean mixed-layer pulse response
function of ocean model (Joos et al.,
1999)
IPCC-TAR methodology
Climate model of MAGICC 3.0
CO2 – For the period from 2012-2040
we assume a linearly increasing
reduction rate. From 2040, onwards,
we use the inverse CO2 concentration
calculations of Enting et al. (1994).
Non-CO2 – Non-CO2 is responsible for a
further 100 ppm, and based on
assumptions about emission reduction
rates (expert judgement).
* A result of the inverse CO2 concentration calculations (methodology)
** Outcome of the calculations
Global terrestrial carbon cycle
model MAGICC 4.1 model
MAGICC 4.1
IPCC-TAR methodology
Climate model of MAGICC 4.1
Calculates mixes of greenhouse gas
emission reductions for a given
global emission pathway under a
least-costs approach based on
iterative process (for more details
see Chapter 2).
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As mentioned earlier, this study focuses more on the lower CO2-equivalent concentration
stabilization levels (400, 450, 500 and 550 ppm CO2-eq.), therefore the only CO2-eq.
concentration stabilization level, analysed in both studies, is the 550 ppm CO2-eq. level,
which we use for the basis of our comparison.
Comparison of the IMAGE S550e and FAIRSIMCAP S550e-CPI pathway (excl. LUCF
CO2 emissions)
Definition of the CO2-equivalent concentration
One of the more important differences between the two studies is the definition of CO2equivalent concentration levels. Where Eickhout et al. only included the six Kyoto
greenhouses gases in the definition, in this study we included all human-induced greenhouse
gases, tropospheric ozone and aerosols, following the IPCC definition (see Schimel et al.,
1997). The effect of the both definitions on the CO2-equivalent concentration is illustrated
for the IMAGE S550e pathway and our emission pathway at 550 ppm CO2-eq. for the CPI
scenario (hereafter known as FAIRSIMCAP S550e-CPI pathway in Figure D.1. Both studies
use the same CPI scenario.
ppm
700
ppm
CO2 -equivalent concentration
700
a. including all GH Gs, tro p O3 and aero so ls
650
b. Including o nly the Kyo to GH Gs
600
CO2 co ncentratio n
550
550
650
a. including all GHGs, tro p O3 and aero so ls
600
C O2 co ncentratio n
500
450
450
400
400
350
350
300
300
2000
2050
2100
2150
2200
time (years)
b. Including o nly the Kyo to GHGs
550
500
250
1950
CO2 -equivalent concentration
250
1950
IM AGE S550e
2000
2050
2100
2150
2200
time (years)
Figure D.1 The CO2-equivalent concentration for the two definitions for the emission
pathway at 550 ppm CO2-eq. for the CPI scenario (FAIRSIMCAP S550e-CPI, left) and
IMAGE S550e pathways (right). The CO2-equivalent concentrations are defined on the basis
of the radiative forcing of: a. all greenhouse gases, tropospheric ozone and aerosols
(Schimel et al., 1997), as assumed in this study; and b. only Kyoto greenhouse gases, as
assumed in Eickhout et al. (2003). Note, for comparison, also the depiction of CO2
concentration (dashed line) for the emission pathways.
By including all greenhouse gases, tropospheric ozone and aerosols, the CO2-equivalent
concentration is presently lower because of the assumed cooling effect of the aerosols, which
is larger than the assumed warming effect of tropospheric ozone. The difference between the
two CO2-equivalent concentration definitions will disappear in future projections because of
the expected mitigation strategies for aerosol emission (directly for reasons for human health
and acidification and indirectly as a synergetic effect of climate policies). Therefore the
impact of different definitions of CO2-equivalent concentration has a minor effect on the
final emission pathway for the 550 ppm CO2-eq. concentration level.
However, the use of the definition has a major impact, in combination with the allowed
overshoot of concentrations, on the emission pathways for the lower CO2-eq. concentration
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levels, i.e. 400, 450 and 500 ppm CO2-eq. With the definition of the inclusion of only the
Kyoto gases as in Eickhout et al., these levels seem to be out of reach, as for example, the
500 ppm CO2-eq. level is already reached around 2025. By including all greenhouse gases,
tropospheric ozone and aerosols in the CO2-equivalent concentration, these lower
concentration targets are possible.
Methods used
The major remaining difference between both studies comes from the different
methodological approaches. The global emissions and the resulting reductions for the
IMAGE S550e and FAIRSIMCAP S550e-CPI pathways are depicted in Figure D.2. This
Figure clearly show that the IMAGE S550e pathway leads to lower emissions of the Kyoto
gases (excluding LUCF CO2) for the period 2025-2045, but at the longer term (after 2050)
the differences between the emissions of both profiles becomes less. More specifically, in
2025 the emissions of the IMAGE S550e pathway are about 22% above 1990 levels,
whereas for the FAIRSIMCAP S550e-CPI pathway emissions are about 30% above 1990
levels.
0
-20
-40
-60
40
A nt. GHG emission reduction f or S550e
IM AGE S550e
compared to baseline
compared to 1990
20
0
-20
-40
-60
-80
-100
60
% change
% change
A nt. GHG emission reduction 550 CO2-eq (CPI)
60
550
compared to baseline
40
compared to 1990
20
-80
Kyo to -gas em issio ns (excl. landuse C O2)
2025
2050
-100
2100
Kyo to -gas emissio ns (excl. landuse CO2)
2025
2050
2100
Figure D.2 Global emission reduction efforts (excluding LUCF CO2 emissions) for the
FAIRSIMCAP S550e-CPI pathway (left) and for the IMAGE S550e profile (right).
Eickhout et al. predefined for the IMAGE S550e pathway a 450 ppm CO2 only concentration
level. The other Kyoto gases are allowed to account for the remaining 100 ppm CO2-eq. In
this study the ‘cost-optimal’ allocation methodology for every 5 year segment of the
emission path leads in the short terms (till 2025) to more non-CO2 reductions, and therefore
higher CO2 concentrations, i.e. at 475-500 ppm CO2. Note again that it is not possible to
judge from the applied methods, which emission pathway is closer to a ‘cost-optimal’
emission pathway over time that dynamically accounts for induced technological progress,
learning effects and system inertia. These differences in the final CO2 concentrations
evidently lead to lower CO2 emissions and higher non-CO2 emissions for the IMAGE S550e
profile. This result is in line with the cost-optimal implementation of the allowed global
emission pathway in van Vuuren et al. (2003; 2004b). The difference in CO2 and non-CO2
contribution to the 550ppm CO2-eq. level impact the conclusions on the emission allowances
in three ways (as also mentioned in Eickhout et al., 2003).
1. Less flexibility for the IMAGE S550e profile – The current CO2 concentration is
already approximately 380 ppm, and this has increased rapidly at a speed of about 30
ppm CO2 over the past 20 years. Without action, the CPI baseline surpasses the 450
ppm target as early as 2030. Not allowing overshoot of the 450 ppm CO2 target
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implies that the rate of increase needs to be reduced quite drastically within this 30
years time frame and, obviously, the amount of flexibility is constraint, leading to
lower CO2 emissions on the short-term; of course, this may be compensated by less
emission reduction hereafter.
2. Fast response of non-CO2 reductions for this study – The early non-CO2 reductions,
in this study lower the CO2-equivalent concentrations directly (Hansen et al., 2000;
Eickhout et al., 2003; Meinshausen et al., 2004; Wigley et al., submitted). This, in
turn, allows CO2 emissions required to match the final CO2-equivalent concentration
profile, to be higher, and the same holds for the overall emissions (see Figure D.2).
3. Slightly enhanced CO2 fertilization effect for this study – Another factor relates to the
terrestrial CO2 fertilization feedback. More specifically, at higher CO2 concentration
levels, plants absorb more CO2, providing a negative feedback that tends to slow
down the growth of atmospheric CO2. The CO2 concentration levels for the
FAIRSIMCAP S550e-CPI pathway are higher, leading to a higher CO2 fertilization
effect. This additional uptake of CO2 by the terrestrial vegetation allows for a modest
additional space of CO2-eq. emissions.
Figure D.2 also indicates that the reductions are even less for 550 ppm CO2-eq. pathways for
the other scenarios (B1 and CPI+tech) (i.e. the FAIRSIMCAP S550e-CPI+tech and S550eB1 pathways), mainly because these scenarios assume lower LUCF CO2 emissions, and thus
the allowed emissions of the Kyoto gases (excl. LUCF CO2) may be higher.
Comparison of the IMAGE S550e and FAIRSIMCAP S550e-CPI pathway (incl. LUCF
CO2 emissions)
IMAGE’s climate model core is built on MAGICC, but IMAGE’s the terrestrial and ocean
carbon cycle models differ from those of MAGICC. This is the main reason why we now
include a LUCF CO2 emissions trajectory excluding the CO2 fertilization effect, otherwise
we would double count this fertilization effect, by accounting this in the calculated terrestrial
carbon uptake of the MAGIC model, and in the assumed LUCF CO2 emissions. The LUCF
CO2 emissions trajectory for the IMAGE S550e pathway, leads to a much higher sink after
2050 compared to the CPI one (depicted in Figure C.2) , i.e. already surpassing the zero
emission by 2050, and finally in 2100, it becomes about -0.8 GtC/year.
0
-20
-40
40
Ant. GHG emission reduction for S550e
IMAGE S550e
compared to baseline
compared to 1990
20
0
-20
-40
-60
-60
-80
-100
60
% change
% change
A nt. GHG emission reduction 550 CO2-eq (CPI)
60
550
compared to baseline
40
compared to 1990
20
-80
Kyo to -gas em issio ns (incl. landuse C O2)
2025
2050
-100
2100
Kyo to -gas emissio ns (incl. landuse CO2)
2025
2050
Figure D.3 Same as Figure D.2, but now including LUCF CO2 emissions
2100
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In the following, greenhouse gas emissions including the LUCF CO2 are compared for the
IMAGE S550e and FAIRSIMCAP S550e-CPI pathways. Figure D.3 shows that the inclusion
of the LUCF CO2 emissions for our FAIRSIMCAP emission pathways leads to fewer
differences among them. This is because the FAIRSIMCAP S550e-CPI pathway’s lower
emissions (excl. LUCF CO2 emissions) compared to pathways based on the CPI+tech and B1
baseline, are now combined with CPI’s higher LUCF CO2 emissions.
Finally, comparing Figures D.2 and D.3 shows that for the IMAGE S550e pathway the
inclusion of the LUCF CO2 emissions leads to much lower emissions, and higher reductions
on the long-term. As aforementioned, this difference is partially reasoned by the differences
in definition of CO2-equivalence.